The fontanelle of 6-month-old babies is a diamond-shaped gap formed by the edge of the parietal bone and the frontal bone, which is 1-2 cm at birth, and increases with the development of the skull later, gradually ossifying and becoming smaller after 6 months, and closing at 1-1.5 years old. Posterior fontanelle is already small or closed at birth, and closes at the latest 6-8 weeks after birth. Prematurely closed or small fontanelles are seen in microcephaly. Late closure or oversized fontanelle is seen in rickets and congenital hypothyroidism. Full fontanelle often indicates increased intracranial pressure, such as hydrocephalus, encephalitis, meningitis, brain tumors, and other diseases. Depressed fontanelle is seen in dehydration and extreme wasting.